Not Applicable.
Not Applicable.
1. Field of Invention
The present invention relates generally to power conversion and, more particularly, to a multiple output power supply including one main output and at least one other output derived from the same switching source.
2. Description of the Background
With the exception of the most simple battery powered devices, all electronic equipment requires some sort of power conversion. Electronic circuitry typically operates from DC voltage sources while the input power to the system is typically in the form of AC power. Furthermore, the end circuitry design of the system is typically optimized to operate from specific levels of DC voltage. Thus, the input power must be converted to specifically required DC voltages.
There are two basic methodologies for accomplishing regulated power conversion. The first is called xe2x80x9clinear regulationxe2x80x9d because the regulation characteristic is achieved with one or more semiconductor devices operating in the linear region. Linear regulators provide the advantages of simplicity, low output noise, fast response times, and excellent regulation. They may, however, be unacceptably inefficient in certain applications.
The second methodology is called xe2x80x9cswitchmodexe2x80x9d conversion which, in contrast to linear regulation, offers the powerful advantage of high efficiency. In this case, the voltage conversion is achieved by switching one or more semiconductor devices rapidly between their xe2x80x9conxe2x80x9d (or conducting) state and their xe2x80x9coffxe2x80x9d (or non-conducting) state such that the appropriate amount of energy is transferred to the load. This principle is called pulse width modulation (PWM). With PWM, the input signal is chopped into pulses, which are averaged to provide a rectified DC voltage used to power the load. PWM is ordinarily realized in converter modules by using a commercially-available PWM integrated circuit (IC) chip. The chip has inputs responsive to the output voltage of the switchmode converter and, based on the detected output voltage, regulates the on and off times of the switching semiconductor device(s) of the converter to thereby regulate the output voltage.
In certain applications, a single power converter module may be required to power loads requiring different, regulated DC voltage levels. Consequently, the power converter modules used to power these various loads typically require a separate PWM chip for each of the required load voltages, which correspondingly increases the cost of the module. Accordingly, there exists a need for less expensive power supply with the capability of supplying multiple DC voltages to a number of loads.
The present invention is directed to a power supply. According to one embodiment, the power supply includes a regulated switchmode converter, a PWM controller, a semi-regulated switchmode converter, and a linear regulator. The regulated converter is for converting an input voltage to a first output voltage. The PWM controller is responsive to the first output voltage, and includes an output terminal coupled to a control terminal of a switch of the regulated switchmode converter. The semi-regulated switchmode converter is for converting the input voltage to an intermediate output voltage, and includes a switch coupled to the output terminal of the PWM controller. The linear regulator is coupled to the semi-regulated switchmode converter and is for converting the intermediate output voltage to a second output voltage.
According to another embodiment, the power supply additionally includes a second semi-regulated switchmode converter and a second linear regulator. The second semi-regulated switchmode converter is for converting the first output voltage to a second intermediate output voltage, and includes a switch having a control terminal coupled to the output terminal of the PWM controller. The second linear regulator is for converting the second intermediate output voltage to a third output voltage.
According to another embodiment, the power supply includes a regulated switchmode converter, a PWM controller, and a linear switch closed-loop switchmode converter. The regulated switchmode converter is for converting an input voltage to a first output voltage. The PWM controller is responsive to the first output voltage, and includes an output terminal coupled to a control terminal of a switch of the regulated switchmode converter. The linear switch closed-loop switchmode converter is for converting the input voltage to a second output voltage, and includes a switch having a control terminal coupled to the output terminal of the PWM controller.
According to yet another embodiment, the power supply additionally includes a second linear switch closed-loop switchmode converter. The second linear switch closed-loop semi-regulated switchmode converter is for converting the first output voltage to a third output voltage, and includes a switch having a control terminal coupled to the output terminal of the PWM controller.
In contrast to prior art power converter modules, embodiments of the present invention provide a relatively inexpensive power supply with the capability of supplying highly regulated DC voltages to number of loads. In addition, the power supplies of the present invention offer a simple, low risk design featuring a number of standard components. Further, the present invention offers an alternative to using transformers, thereby offering a less complex overall design.
These and other advantages of the present invention will be apparent from the detailed description hereinbelow.